docs: def interaction_columns_used(self):
          """
          Columns from the interaction dataset used for filtering and in
          the model. These may come originally from either the choosers or
          alternatives tables.
  
          """
          return list(tz.unique(tz.concatv(
              util.columns_in_filters(self.interaction_predict_filters),
              util.columns_in_formula(self.model_expression))))